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Full text of "Circuits"

Circuit-Bend Your Casio SK Keyboard 



Makej Projects 



Circuit-Bend Your Casio SK 



Keyboard 

Written By: Cristiana Yambo 



TOOLS: 

• Drill and drill bits (1) 
Electrical Tape (1) 
Glue gun and hot glue (1) 
Multimeter (1) 

Multiple voltage transformer (optional) 
(11 

Rotary tool and bits (1) 
Soldering equipment (1) 



PARTS: 

Casio SK-series keyboard (1) 

We used an SK-5. but they're all great 

for bending. Check local thrift stores or 

eBay. 

Stranded wire 22- gauge or thereabouts 

in 

Small machine screws and nuts (1) 

At least 77 of each. 

Flat non-conducting easily drillable box 

in 

For the patch bay, we used a translucent 

plastic storage box. The patch bay box 

should be big enough to hold and permit 

access to 77 screws without crowding. 

Flat non-conducting box (1) 

Like above, but smaller: for external key 

box controller (optional) 

Assorted switches contacts and other 



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Circuit-Bend Your Casio SK Keyboard 



bend components (1) 

For the control panel. We used 4 toggle 

switches. 1 potentiometer, 1 photometer. 

2 doorknobs (for body contacts), and a 

pushbutton momentary switch to reset 

the device. 

Flat non-conducting easily drillable panel 

about 5"x5" (1) 

For the control panel, which fits over the 

keyboard's speaker area. 

Hose clamps (2) (1) 

Alligator clips (1) 

At least a few; the more, the merrier. 

Ethernet cabled) 

For external controllers (optional) 

Ethernet jack (1) 

For external controllers (optional) 

Flexible plastic tubing (1) 

Momentary switches (1) 

We used keyboard keys from an old 

Macintosh. In many older, heavier 

computer keyboards, each key is its 

own selfcontained momentary switch 

(not shown). 



SUMMARY 

By Cristiana Yambo and Sebastian Boaz 

The easiest way to start circuit bending is "playing open circuits." That's where you open up 
an audio device and use your hands or alligator clips to mess with the board inside and see 
what it sounds like. But it's almost as easy to permanently "bend" any suitable device by 
soldering on a few wires and switches. We'll explain how, and then show you how we 
transformed a Casio SK-5, a common, 80s-era sampling keyboard, into an unstoppably 



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Circuit-Bend Your Casio SK Keyboard 

flexible sound organ and sonic effects generator. 

A word of caution: Do not attempt to circuit bend anything that needs to be plugged into a 
wall, such as a VCR or a television. These devices use high voltages, and playing with the 
circuitry inside might injure or kill you. Circuit bending is for battery-powered toys and 
instruments only. 



Step 1 — Connect the patch wires. 








• The chips on Casio SK keyboards contain vast potential for unruly sounds, and 
wiring up a patch bay unlocks all of it by making every possible pin-to-pin 
connection available. 

• Find the main chips. Open the case, remove the motherboard, and identify the main sound 
processing chips; these are two large, rectangular chips next to each other in the middle of 
the board. Each has 14 pins per side, a total of 56 pins. Turn the board over and find the 
points of these pins on the underside. You will solder one wire to each of these. 

• Solder and check wires. For each row of 14 main chip pins, solder 14 lengths of wire, each 
around 30 inches long, to the contact points underneath. Carefully check each pin for 
solder bridges. When you finish a row, replace the board and play the keyboard to see if it 
still works normally. If it makes any weird sounds, you probably bridged two pins together. 
You can also use your multimeter to test pairs of wires for continuity and resolder 
wherever you find one. 

• Insulate. Once each row passes its test, cover its pins in electrical tape, and wrap the 
wires in electrical tape to create a nice cable. After you've soldered and checked all four 
rows, remove the tape covering the pins and test the unit again. When it passes the test, 
warm up your glue gun and cover each row in hot glue. This holds the wires in place and 
insulates the connections to prevent unintended short circuits. 



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Circuit-Bend Your Casio SK Keyboard 



Step 2 — Build and connect the patch bay. 




• Some people construct patch bays using RCA jacks, but screws and alligator clips 
are cheaper, more compact, and they let you connect multiple clips to the same 
point, which vastly expands the sonic possibilities. 

• Drill the holes. Measure, mark, and drill 60 holes in the patch bay box, four rows of 15, one 
for each of the 56 wires, plus four jumper points on the side to facilitate multiple 
connections. The holes should fit your screws snugly. Leave room for another, smaller set 
of holes for the control panel which you'll drill later. 

• Insert the screws. Bolt screws into the holes, with the heads on the inside and the shafts 
pointing out. 

• Make the patch cable. Count your control panel components, and then strip and cut 
enough wires to connect to each of these, plus two more for the tuning circuit; we used 17 
total. You'll connect these wires later, so it helps to include some extra ones and label 
which ends connect to one another. Gather them together with four taped-together sets of 
patch wires, to make a super-cable that will run between the keyboard and patch bay. 
Secure each end with hose clamps, and push it through the plastic tube. 



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Circuit-Bend Your Casio SK Keyboard 



Step 3 




• Route the patch cable. Cut a large hole in the side of the patch bay box. Insert the patch 
cable and secure it by hot-gluing the hose clamp to the box. 

• Connect the patch wires. Now it's time to wire the screws. Wrap the end of each patch 
wire clockwise underneath the head of each screw and tighten the bolt to secure the wire. 
Connect each group of 14 patch wires to a different row on the patch bay. 

• Test the board. Using alligator clips, connect switches and pots between different patch 
points, play the keyboard, and see how it works. Operating the components and changing 
their configuration should yield different sounds. 



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Circuit-Bend Your Casio SK Keyboard 



Step 4 — Remove the tuning pot. 



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• Many old electronic instruments easily lose their tuning and have a small 
potentiometer that adjusts them back into tune. We'll bring this component's 
connections out to our patch bay, so you can create bends that alter the pitch of the entire 
keyboard. 

• Unsolder the pot. The SK's tuning pot is normally accessed through a hole in the underside 
of the keyboard, in the center, and you adjust it with a small screwdriver. Find the 
component on the board and use a solder sucker or desoldering braid to remove all of the 
solder. 

• Pull out the tuning pot. You will probably have to use some force. Then mark where it was 
located, to help you find it later. 



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Circuit-Bend Your Casio SK Keyboard 



Step 5 — Build the control panel. 



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The control panel houses interface components which you can hook into any circuit 
bends via the patch bay. It also has the reset button, a momentary switch that 
restarts the instrument after a crash. 



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• Using a rotary tool, cut out the speaker grill. This hole is going to be used to house the 
interface elements. 

• Build the control panel. Attach your components to the panel. For ours, we drilled holes in 
a piece of hard plastic and then hot-glued in our components: four toggle switches, a pair 
of doorknobs for body contacts, a potentiometer (separate from the tuning pot), a 
photometer for lightsensitive distortions, and a momentary switch, which will act as a reset 
button. 



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Circuit-Bend Your Casio SK Keyboard 



Step 6 — Connect the control panel. 




• Finish the patch bay. Drill holes and install screws in the patch bay, as in Step 2. You'll 
need the appropriate number of contact points for each component on the control panel, 
plus two more to lead to the tuning pot's contacts on the circuit board. Arrange the holes in 
the same way that your components are arranged on the control panel. This makes it easy 
to remember which contact point on the bay corresponds to which control. 

• Wire the control panel. Now you're going to use the extra wires in the cable. If they aren't 
labeled, use a multimeter to identify matching ends. Then connect the control panel 
components to the new patch bay array, following your logical mapping. Screw the wires to 
the patch bay points as before, and solder the other ends to the components. 

• Connect the tuning circuit. Screw two remaining extra wires to the tuning-circuit points on 
the patch bay and solder the other ends to the tuning pot contacts on the board. 



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Circuit-Bend Your Casio SK Keyboard 



Step 7 — Connect the reset, and close it up. 




• Bent instruments sometimes crash in a way that disables the power switch. One 
solution is to wire a momentary switch between the positive power line and the 

circuit board, but with the SK-5 it's easier to install a switch that connects the positive and 
negative power lines, momentarily shorting them out. 

• Connect the reset button. Solder the reset button's contacts to the positive and negative 
terminals that lead from the battery compartment. 

• Hot-glue the control panel to the case. 

• Close up the case. Screw it together, switch it on, and then rock out with the ultimate SK! 

• Extend the capabilities of your new keyboard by adding an external controller port 
and making two kinds of external controllers. Visit makezine.com for complete 
instructions. 



2 



This project first appeared in MAKE Volume 04 , page 88. 



This document was last generated on 201 2-1 1 -03 03:48:39 AM. 



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